The invention relates to a method of communication in a network comprising so-called non-wired nodes provided with communication means enabling communication by non-wired channel and so-called wired nodes provided with communication means enabling communication by wired channel and by non-wired channel. It also relates to a network for implementing this method.
Having the various elements of a home automation or building automation network communicate via wireless links by radiofrequency waves or by infrared waves is known. The use of such wireless communication links is recognized for the flexibility and ease of installation that it provides. However, the range of such links can be limited, particularly in the case of transmissions through partitions, walls or ceilings.
In the case of installations where such problems arise, the use of repeater elements is routine, so as to ensure the transmission of information between the various elements of the network despite the presence of obstacles. However, the installations provided with repeaters have drawbacks such as the increased information transmission delays and the spectrum usage time.
Another solution involves using a supplementary cable network to route the information from one room of the building to another. The range of the wireless links needed is then limited to the distance between the elements communicating only via wireless links and the nearest element linked to the cable network.
The main characteristic of the known installations using repeater elements is to provide and transmit, at the same time as control information for an equipment item in the building, a certain number of information items needed to route the data.
Patent application WO 01/78307 describes a home automation network in which any controlled equipment item can become a repeater. Thus, an equipment item can receive signals transmitted by different routes using the existing controlled equipment items. In this network, routing tables are duplicated from one repeater equipment item to another in an adjustment mode. In this way, it is possible, for each equipment item, to initialize a routing table, enabling it to receive information and retransmit it to another equipment item by radio link.
Along the same lines, patent application WO 02/098060 describes a method of identification, by an element, of the various elements of the network that surround it, by constructing a table of identifiers that can be recipients of a message.
A method of dynamically determining the length of the path traveled by a message, so as to optimize the communication times by favoring short paths, is known from U.S. Pat. No. 5,875,179.
In the field of access control by reading magnetic cards, a communication network comprising repeater elements operating on the principle of routing and means for modifying the routing signal if return information from a recipient element to which a message is transmitted is not received within a given time, is known from U.S. Pat. No. 4,912,461.
Finally, from U.S. Pat. No. 5,905,442, a system in which the elements can communicate by different types of link is known. Claim 105 defines a transmission mode wherein a state modification control instruction is transmitted via a wired communication link and wherein the return information is transmitted via a wireless communication link.
Similarly, systems managing the interactions between wired and non-wired communications are described in the Japanese patent applications JP 2003-134030 and JP 2001-156804.
Application JP 2003-134030 describes in particular a cable network, to which is added a radio function and a wire/radio protocol conversion function to add flexibility to the system. The redundancy of the communication paths is, in this patent application, one means of increasing the reliability of the system.
Application JP 2001-156804 also describes a system wherein the nodes of the cable network can act as repeaters to transmit a communication between two non-wired nodes.
None of these documents provide for a measurement for checking that each receiving node receives the transmitted message only once, possibly by different paths.
On the contrary, to provide a good transmission reliability, favoring a systematic reproduction of the signals transmitted over supplementary (cable) networks is routine. Such is the case for example in document JP 2003-134030. Because of this, it is possible for certain controls to be received and interpreted several times, which poses problems in the case of sequential controls for example. Furthermore, the system can experience spectrum management and occupancy problems.
A somewhat similar problem can be found in U.S. Pat. No. 6,690,276. In this patent, the aim is to monitor the data transmitted over a communication bus between a central processing unit and receivers. When a receiver receives a message from a wireless transmitter, it translates it into a digital signal and transmits it to the control unit. The latter, on receipt, sends a confirmation message. A second receiver receiving a message from a transmitter places it in a memory. It then listens for a confirmation message, if any. If it receives one, it checks whether the first message is identical to that which it has in memory. If it is, the memory is erased; otherwise, the second message is transmitted to the control unit. This U.S. Pat. No. 6,690,276 therefore proposes a solution to avoid the duplicated transmission of one and the same message from different sources to one central unit over a wired bus, so as to avoid unnecessary signal traffic on the cable network. It therefore does not provide any response in the context of a system in which repeater elements need to be sure of routing a message just once when there is a plurality of different paths (wired or non-wired) to a receiving node.